Conventionally, a baffle plate made of a metal is attached to an oil pan by welding or bolting to inhibit rocking of a liquid surface of an oil (oil surface) in the oil pan of an engine, and to prevent occurrence of air bubbles in the oil.
However, such a baffle plate is fixed to the oil pan, and therefore, cannot sufficiently respond to the fluctuation of the oil surface in the oil pan. Therefore, Patent Literature 1 proposes to place a plate-shaped float in an inside of the oil pan, which covers the oil surface of this inside. The float is configured to contain a core member of a metal in a styrene foam, and form a through-hole therein.
Further, Patent Literature 2 discloses that a float member is floated on an oil surface in a tube casing attached in an oil pan. The tube casing is porous, and is attached to the oil pan substantially perpendicularly to the liquid surface by using a fixture so as to surround the float member from four sides. The float member includes a porous sheet of sponge or the like, a foamed sheet as buoyancy means which is affixed on a top surface of the porous sheet, and a wire gauge for reinforcement which is affixed on an undersurface of the porous sheet. The float member is provided with a hole for an oil strainer to pass through, and in particular, the foamed sheet is provided with a plurality of air bubbles and a plurality of oil drop holes over the entire surface thereof.
Further, Patent Literature 3 discloses that a plurality of float members which are connected to each other are floated on an oil surface in an oil pan so as to enhance followability to rocking and waviness of the oil surface in an oil pan. The plurality of the float members are connected to a wire-shaped locking member having both ends connected and fixed to an oil pan inner wall surface. More specifically, each of the float members is attached to the lattice point at which two locking members intersect each other to have gaps from the other float members.
Furthermore, Patent Literature 4 discloses to provide a number of floating bodies in an oil pan, which are composed of small pieces of particulate matters with the specific gravity smaller than that of the oil, to cover the entire area of the oil surface. The floating bodies have, for example, spherical shapes with diameters of 10 to 20 mm, or cubic shapes.